History and politics often have unexpected twists but François Hollande's victory in the decisive second round of France's presidential election on 6 May 2012 is not one of them. The margin may have been tinier than opinion-polls estimated - 51.6%-48.3% over Nicolas Sarkozy, the same result achieved in 1981 by the only previous socialist president, Hollande's mentor François Mitterrand; but the result belongs to a pattern in which the Socialist Party (PS) has won every local and European elections since 2004, losing "only" the two that matter, the 2007 presidential and legislative ones. The left now for the first time controls the senate, most main cities, a majority of departments and all but two of France's metropolitan regions. So, it was logical that its candidate would at last, on 15 May, enter the Elysée palace, when Sarkozy says he will leave political life.

Hollande was not initially the PS's favoured candidate. The one anointed one as its "best choice" to defeat Sarkozy was the flamboyant former IMF head Dominique Strauss-Kahn, whose immoral (if not illegal) sexual frolicking destroyed his chances. Yet charges by the right that Hollande was a default candidate are incorrect, for he had announced his candidacy almost two years earlier - to the chagrin of "DSK", who had threatened to wipe him out of the political world if he did not withdraw.

It was but the latest example of the folly of underestimating this loner with only a few close friends, who at the age of 16 had declared that he wanted to be president. Some "friends" in his own party had long despised a man they called "Flanby" (a brand of jelly). Nicolas Sarkozy, too, boasted that he would atomise this gutless weakling who would, he said, "dissolve himself as a sugar cube in a glass of water". Then, most media outlets and pundits - French and international, notably the British press - lambasted him as a boring candidate leading an even more boring campaign...which ended with enthusiastic rallies and an 80% turnout.

The two campaigns

It turns out, however, that the calm, even (yes) boring François Hollande seems to be what a majority of French voters want after five years under a chaotic, egocentric, bling-addicted president who had made so many promises he proved unable to fulfil (such as lowering unemployment to 5%). Hollande's pledges by contrast are few and modest - though even they (such as reforming the state's finances without slashing the welfare state) will be hard to implement, and the attack on his proposal to allow those who had worked for forty-one years to retire at the age of 60 (caricatured by Sarkozy and the media as "retirement at 60 for all") may be a foretaste of struggles ahead.

The socialist candidate ran a well-judged campaign by both solidifying a divided left (including his own party) and extending his hand to the political centre. The centrist leader François Bayrou may disagree with Hollande's economic strategy, but his revulsion at Sarkozy's courting of the National Front led him for ethical reasons to declare support for Hollande in the second round. This, the first such rapprochement between left and centre for a long time, led 30% of Bayrou's followers into Hollande's camp - which, along with a sprinkle of around 15% of disenfranchised Le Pen voters to win against the incumbent president.

For his part, Sarkozy was too arrogant to admit that the man who had quietly prepared himself to fight him to the finish, and who never strayed an inch from his platform, even had a chance. "Sarko" started late, then ran an improvised campaign whose somersaults were unpalatable to many voters (centrists especially). The president's xenophobic (anti-Muslim, if not racist) "belly-dancing" to attract supporters of the FN, and his occasional anti-European Union statements (such as the TV ad showing a road sign with the word "border" written in French and Arabic) were strange enough for a leader so eager to establish strong links with rich Gulf states, but they also alienated significant constituencies.

Sarkozy in the end fought the wrong campaign, compounding the error of his UMP party in giving itself to the wrong candidate. The French rejected the man more than what he stood for. It seems very possible that another UMP figure, such as outgoing premier François Fillon or foreign minister Alain Juppé, would have had a good chance of upsetting Hollande (something the conservative daily Le Figaro belatedly ackowledges on the day after the vote).

The short honeymoon

The right points out that the result was closer than many predicted, but a victory is a victory (and the difference of 1.1 million votes was greater than the 0.4m by which Giscard d'Estaing defeated François Mitterrand in 1974). But a crucial third round remains: the parliamentary elections in June 2012, where Hollande needs a majority in order to govern. French voters usually grant one to their new president, but the right has already started to warn against what it already calls a "left-wing monopoly" and to seek a new "cohabitation" (as in 1997 between Jacques Chirac of the UMP and a socialist premier, Lionel Jospin).

Hollande faces a tough battle to control both houses of parliament, but for the now orphaned UMP - deprived of its natural, omnipresent and omnipotent leader - the task is equally hard. Its rivalries, personal and ideological, are already visible, especially between the hard-right Jean-François Copé (who controls the party machine) and François Fillon, while Alain Juppé is offering himself as a unifier. The party's moderates are no longer afraid to express shock at Sarkozy's move towards the FN's ideology, whereas some on its "popular right" - ignoring the fact that Sarkozy's hardline strategy contributed to the result on 6 May - dream of an alliance with the FN. Marine Le Pen, the FN leader, will do her utmost for an UMP defeat as she did for Sarkozy's, hoping to build a new party on its ruins which would become the official opposition to the left.

There are further reasons why Hollande can't count on a long honeymoon ("One night would be great", someone said). After announcing his new government he will fly to Berlin to meet German chancellor Angela Merkel to discuss his proposal of supplementing the last European treaty with a "growth pact" that offers a fresh dimension amid financial, economic and social rigour; then to Washington for crucial G8 and Nato summits, where he will inform President Obama of his decision to withdraw French forces from Afghanistan before the end of 2012; then in June to the G20 summit in Mexico and an EU summit.

Hollande knows he needs growth to fight France's massive unemployment and outsourcing and to give some hope to the millions who voted for him, including the 49% who think the economic situation can't but deteriorate. The aspiration also fits his emphasis on ethical behaviour (a jab at Sarkozy), on justice and fairness for all, and on the importance of giving a future to a young generation hit even harder by unemployment and a deteriorating educational system.

Hollande's growth strategy (and his linkage to it of deficit reduction) was bitterly criticised during the campaign by Sarkozy, Merkel and many experts, who see it as idealistic at best. But the extension of the crisis to Spain and the Netherlands (the "good pupil"), the ongoing downfall in Greece, and the systematic ousting of European governments - Sarkozy is the eleventh since 2008 - has changed the picture. More instritutions, including Italy and Spain's governments, the European central bank and even Brussels, as well as the World Bank and the US treasury, have moved towards Hollande - who now looks more like a witty precursor than a nincompoop or a socialist of yesteryear. Even Berlin now admis the necessity of growth. Though the meaning of any European "new deal" remains different for every EU country.

The new president

The campaign has changed the man. Although he remains modest in appearance, he appears to have grown into the size of his presidential suits and acquired more legitimacy and authority along the way. He has even managed to subdue factional rivalries within his own party, long nicknamed a machine à perdre ("losing machine").

But it is easier to draft an election platform than to implement it, not least in the context of the dramatic situation France and Europe are muddling through. Will François Hollande succeed, especially in his ambition to unify the French people - something no president has been able to achieve since Charles de Gaulle in the early 1960s; or will he be forced by his hard-left allies to move more in their direction and thus alienate his moderate supporters?

In any event, he knows well the comment attributed to Léon Blum, socialist prime minister in the Popular Front government of 1936: Maintenant les difficultés commencent ("The difficulties are just beginning"). As for myself, I would not like to become the fifth in line to underestimate François Hollande!